Ultrahigh frequency travelingwave tube power regulating system



Sept. 23, 1952 P. M. LAPOSTOLLE 2,61

ULTRAHIGH FREQUENCY TRAVELING-WAVE TUBE POWER REGULATING SYSTEM Y FiledJuly 26, 1951 8 Sheets-Sheet 1 Y ERRE MARCEL LAPUST'OLLE.

mveurox AGENTS.

Sept. 23, 1952 P. M. LAPOSTOLLE 2,611,832

ULTRAHIGH FREQUENCY TRAVELING-WAVE TUBE POWER REGULATING SYSTEM FiledJuly 26, 1951 8 Sheets-Sheet 2 HERRE MAME; LA'POSTOLLE v INVE-NToR 3y+40.

AGENTS Sept. 23, 1952 P. M. LAPOSTOLLE 2,611,832

- ULTRAHIGH FREQUENCY TRAVELING-WAVE TUBE POWER REGULATING SYSTEM FiledJuly 26, 1951 8 Sheets-Sheet 3 k E E 3 a Lt -&

Till! ks 3 g 2 AQEMTS Sept. 23, 1952 P. M. LAPOSTOLLE 2,611,832

I ULTRAHIGH FREQUENCY TRAVELING-WAVE TUBE POWER REGULATING SYSTEM FiledJuly 26, 1951 8 Sheets-Sheet 4 2-, L: 1| iii l 5 s: E \M S QC:

l l l "PERRY. MARcEL LA'POSTOLLE my EN'ToR v ,LTIWIW/IW 0.

AGENTS 8 Sheets-Sheet 5 P. M. LAPOSTOLLE POWER REGULATING SYSTEMULTRAHIGH FREQUENCY TRAVELING-WAVE TUBE Se t. 23, 1952 Filed July 26,1951 JINVENTD K 31 M 1 a.

' AGENTS WERE MARCEL LAPosToLLE Sept. 23, 1952 P. M. LAPOSTOLLE2,611,832 ULTRAHIGH FREQUENCY TRAVELING-WAVE TUBE POWER REGULATINGSYSTEM Filed July 26, 1951 8 Sheets-Sheet 6 HERRE MAME}. LAP08TOLLEINVENTDR p 1952 P. M. LAPOSTOLLE 2,611,832

' ULTRAHIGH FREQUENCY TRAVELING-WAVE TUBE POWER REGULATING SYSTEM FiledJuly 26, 1951 8 Sheets-Sheet 7 MR mmicit LA'POSTOLUi IMVENTDR v 57Hum,-/-+Z..

. AEEMTS Sept. 23, 1952 P. M. LAPOSTOLLE ULTRAHIGH FREQUENCYTRAVELING-WAVE TUBE POWER REGULATING SYSTEM 8 Sheets-Sheet 8 Filed July26, 1951 &

'PIERRE MARQE APos'roLLi R n. w u m W/WE m By mm Patented Sept. 23, 1952ULTR-AHIGH FREQUENCY TRAVELING- WAVE TUBE POWER SYSTEM REGULATING PierreMarcel Lapostolle, Saint-Germain-en- Laye, France Application July 26,1951, Serial No. 238,651 In France August 7, 1950 8 Claims.

This invention is for improvements in or relating to a system forregulating the power of output signals and in particular for ultra-highfrequency amplifiers and has for one of its objects the provision of aregulating arrangement in which one or more traveling-wave amplifyingelectron tubes are employed and which operates directly at ultra-highfrequency, by making the gain of the tube or tubes dependent upon theultra-high frequency energy received at the output end of thearrangement, through a circuit hereinafter referred to as a feedbackloop, the arrangement possessing particular properties due to a periodicauxiliary amplitude modulation to which the signal, the power of whichis to be subsequently regulated and which is applied to the input end ofthe arrangement, is subjected before its amplification by the amplifyingtube or tubes. The frequency of this auxiliary modulation is a lowfrequency and is in any case lower than the lowest modulation frequencypresent in the signals to be regulated.

A further object of the present invention is to provide a regulatingarrangement independent of the precise characteristics of the elementsof the said feedback loop.

It must be clearly understood that it is assumed that the usefulmodulation of the ultrahigh frequency signals which it is desired toamplify is generally a frequency modulation or a phase modulation,since, having regard to the lack of amplitude linearity oftraveling-wave tubes, the employment of amplitude modulation wouldafiordserious disadvantages.

The theory and the construction of travelingwave tube have'beengenerally described notably in a paper by John R. Pierce and Lester M.Field, entitled Traveling-wave tubes, published in the journal,Proceedings of the Institute of Radio-Engineers, vol. 35, page 108 etseq., February' 1947. It will merely be recalled here that such a tubecomprises essentially an electronemitting cathode, an electrode assemblyserving to form an electron beam and called an electron gun, comprisingnotably one or more accelerating electrodes hereinafter called firstanode, second anode, etc., a helicoidal transmission line (or moregenerally, low propagation velocity transmission line) within which thebeam passes, hereinafter more briefly called helix, and an electrode forcollecting the electrons of the beam. It is known that the gain of thetube depends primarily on the mean potentials with respect to thecathode, of the accelerating electrodes and of the helix.

2 In order to achieve the object of the present invention, employment ismade of the fact that the characteristic output power-input power curvesof most types of travelling-wave tubes at 1 different values of thehelix voltage and a constant first-anode voltage have maxima ofsubstantially constant value. The characteristic method of the presentinvention thus consists in applying, by means of suitable low-frequencymodulating voltage and modulating agency, an amplitude modulation to thesignal to be regulated prior to its application to the input of theamplifying tube and in automatically adjusting the helix voltage to thevalue at which the output power corresponding to the mean value of thepower of the inputsignal thus modulated is a maximum one. This is doneby employing the characteristics of the modified low-frequencymodulation which is found at the output from the amplifying tube and,more specifically, the relationship of the phase of the so modifiedmodulation to the phase of the amplitude modulation of the signal at theinput of the amplifying tube or to that of the above-said modulatingvoltage. The method employed in accordance with the present inventiontherefore differs from the known regualting method in which alowfrequencymodulation introduced into the amplifier tube itself or intothe output circuit thereof is employed. This particular arrangement is,in

fact, necessary for permitting .an effective reg-ulation, not in respectof the accidental variations of the feed voltages of the tube alone, butalso, and above all, in respect to considerable variations .of the powerof the signal applied'to its input.

A variation of the invention isapplicable ,to

the case of certain types of traveling-wave tubes in which the maxima ofthe output power at different values of the helix voltage and a-constantfirst-anode voltage have not a constant value. It is then generallypossible to find pairs of helix voltage-first anode voltage values, withwhich these maxima are substantially constant. The characteristic methodof the present invention consists, in this case, in applyingan amplitudemodulation to the signal to be regulated previously to its beingamplified by .the traveling-wave tube, and in automatically andsimultaneously adjusting both helixavoltage and first-anode voltage tothe values at which the output power corresponding tothemean' value ofthe input signal thus modulated is; a maximum one. v

Further objects and features of- 'thejpresent invention will be moreparticularly described with reference to the accompanying drawings inwhich:

Figure 1 illustrates the characteristic output power-first-anode voltagecurves of a travelingwave tube for different values of the input power.

Figure 2 illustrates the characteristic output power-input power curvesof a traveling-wave tube for different values of the helix voltage inthe case where the maxima of these characteristics are constant for acommon first-anode voltage,

Figure 3 illustrates the characteristic output power-input power curvesof a traveling-wave tube having constant maxima for different pairs ofhelix voltage-first-anode voltage values,

Figure 4 illustrates an arrangement of a previously known type forregulating the power of a traveling-wave tube,

Figure 5 illustrates a regulating arrangement according to subjectmatter of the present invention,

Figure 6 illustrates diagrammatically the details of a phase detectorwhich is an essential part of the system, the object of-the invention,

Figure 7 illustrates a two-stage regulating arrangement,

Figure 8 illustrates a; modified form of the previous two-stageregulating arrangement, and

Figure 9 illustrates the characteristic output power-input power curvesof a traveling-wave tube for different pairs of helix-voltage andfirstanode voltage values in the case where these characteristic curvescorresponding to a commonhelix voltage and to different first-anodevoltages intersect one another.

Although the present invention does not necessitate the use oftraveling-wave tubes of any particular type, the present description hasbeen based on tubes of aparticular type including a special method. ofconnection of input and output circuits, but this does not to any extentlimit the scope of the invention.

Referring to the drawings and in particular to Figure. 1, there isillustrated, as a function of the voltageappliedtothe first anode Va ofa traveling-wave tube, the value of the'output power of this tube atdifferent values of the input power and for a constant helix voltage. Itwill be seen from Figure 1 that if the voltage of the first anode isvaried ata frequency f, for example sinusoidally; there is obtained atthe. output end of the tube a signal amplitude-modulated at this samefrequency ,1 around a certain mean value depending upon the power of theinput signal. If, for example, the voltage of the first anode issinusoidally varied at the frequency I about the value 50 volts, theoutput power is modulated about 13 milliwatts if the input power is lmilliwatt and about 1.5 milliwatts if the input power is 0.1 milliwatt.

Figure 2 illustrates, as a function of the input power We applied to thetraveling-wave tube, the power Ws obtained at its output for variouspotential differences applied between the cathode and the helix. It willbe assumed for the instant that the electron-optical system of the tubeis such that, regardless of the potential difference between the cathodeand the helix, the cathode current and the current of the collectingelectrode are constant. Under these conditions, the curves such as 2|,22, 23, 24, 25, 28 and 21 corresponding to different helix voltages, forexample 1500, 1475, 1450, 1425, 1400, 1375 and1350 volts'and to aconstant first-anode-volt- 4 age, for example volts, each have a.maximum and these maxima are the same, for example milliwatts in theexample illustrated.

Regardless of the ultra-high frequency power applied to the input of thetube, it will be seen that there exists a voltage applied to the helixat which the output power passes through a maximum, the first-anodevoltage being maintained constant.

For an input power of 1 milliwatt, for example, the output power-passesthrough a maximum of 100 milliwatts if a potential difierence of 1500volts is applied between the cathode and the helix. If the input powervaries by 1- 50% of 1 milliwatt, the output power does not vary by morethan 3% for this same helix voltage and the output power variationswould be only 0.03% if the input power varied by i- 5%.

The combination of Figures 1 and 2 shows that if the first-anode voltageof a traveling-wave tube is varied, for example sinusoidally, there isobtained for a given input signal an output signal amplitude-modulatedabout acertainmean value and that if this amplitude-modulated signal isapplied to the input of a second travelingwave tube, there :exists'for'thissecond. tube a helix voltage at which the output'signal powerpasses through a. maximumv value. By making the helix voltage of the.said second-tube dependent upon the meanvalue of the input signal of thesame tube, alimiting arrangement is obtained.

In order clearly to illustratethe difference between the arrangementaccording tothe present invention and'a simple automatic gain-controlarrangement, such as can be simply obtained at ultra-high frequency, anarrangement of the latter type will be described withreference to Figure4.. .It will berecalled that the latter arrangement is no part of theinvention.

In Figure 4, there is illustrated a travelingwave tube 400, having acathode 40!, accelerating electrodes or first and second anodes: M32-and 493 of the electron .gun, a helix 464, hollow cylindro-conical endmembers405 and 306 for the adaptation of the input and outputcircuits-to the helix 404, a target 40? collecting the electrons of theelectron beam after they have passed through the interior of the helix304-, coaxial input and output lines1408. and- 409for. the signal,conductive plates 4H! and 4H capacitively coupling the internalconductors of the said coaxial lines with the. cylindro-conical' endme'mbers,'405 and 406, a screening M2 towhich the outer conductors ofthe coaxial lines i08 and 400 are'connected, and a magneticbeamfocussing coil M3.

An alternating current-source 4 I 4' is employed for heating the cathodewhile-batteries H5,- H6

and M! are employed for feeding respectively the first anode: 402, thesecond anode-603, the

helix -lM'and the'targe't 407 bynieans of connec-- tions, 436, 431, '438and'439; Thecathode flill is connected to the negative terminal ofL HS'by the'connection 435.

An input ultra-high frequencysignal is applied to the line 408. Afraction of: the amplified'signal power is derived from the outputlinclflfi by a loop 452. and detected by a. de'tector453. Thedirect-current voltage from'this detector is amplified ina..direct.-current amplifier AEQ-and added with a suitablesign to thepotential-of one of the electrodesof thetubewhich control'the gainthereof. .The voltage thus detected-and amplified. may be applied tothe. helix 404, in

which case the connection 438 is opened at '442 and line 446 isconnected to points indicated at 443 .and444, line 445 being omitted.

The same detected and amplified voltage ma be applied to a first anode,in which case the connection 436 is opened at the point indicated at 440and the line 445 extended by the line 445 is connected to the points MIand 447. No connection then exists at the points 443 and 444. 7

Considering, for example, the case where the detected and amplifiedvoltage is applied to the helix of the tube, it will be seen that theregulating system described is simply a linear control system. The powerof the input signal being, for example, 5 milliwatts and the helixvoltage 1475 volts, the representative point is at A and the outputsignal has a power of 70 milliwatts. As the input signal increases andreaches, for example, the value 8.5 milliwatts, the representative pointmoves from A to A on the characteristic curve 22. The power of theoutput signal falls to 50 milliwatts. Simultaneously, the voltageapplied to the helix decreases.

The point B corresponding, for the new input power of 8.5 milliwatts, toan output power of 70 milliwatts is situated on the curve 28 of thehelix voltage of 1455 volts. It will be assumed for the sake ofdefinition that the characteristic curves of the feedback loopconstituted by the loop 452, the detector 453 and the amplifier 459 aresuch that if the output power falls from 70 milliwatts to 50 milliwatts,the helix voltage falls precisely from 1475 volts to 1455 volts. Therepresentative point of the operation returns, under the action of theregulating system, from A to C between A and B, the point Ccorresponding to a new output level of 60 milliwatts on the curve 29 ofthe helix voltage of 1465 volts.

It will be seen that, according to whether the gain of the amplifier 459is higher or lower, the variations of the output level of the tube 405are more or less reduced with respect to those of the input level, butthe output level necessarily varies in the same direction as the inputlevel because an error voltage (voltage across the output terminals of459) is required to control the regulating system.

However, the output level essentially depends upon the characteristiccurves of the loop452, of the detector 453 and of the amplifier 459.

Now, the detectors employed at ultra-high frequency, while havingsufiicient stability for other applications, are far from possessingconstant characteristicv curves. On the one hand, these characteristicsvary with temperature and even sometimes simply with time. On the otherhand, a very considerable dispersion exists between the individualcharacteristics of a number of detectors. This dispersion not onlyaffects the detection output but may also take effect by the impedancepresented at ultra-high frequency to the fraction of energy caught bythe loop 452. If the precaution is not taken of making a number ofdelicate adjustments at the time when a detector is replaced, thearrangement described may provide, at the output, ultra-high frequencysignal levels varying within a wide range, which may easily reach 10decibels.

Moreover, if the traveling-wave tube 455 is replaced by another tube, itfrequently happens that all the characteristic curves of Figure 2 aredisplaced to the left or the right while the maxima of the differentcurves retain a value which is remarkably constant for difierent tubesof similar construction. On Figure 2, the displacement of all thecharacteristic curves by a move-' ment of the axis. ofhtheoabscissae 0W5now occupying the position OlWe isillustrated.

With the first tube, the point A corresponds to an voutputlevel of 70milliwatts. and to a helix voltage of 1475 volts. The characteristiccurves of the feedback loop are suchthat if the output level falls to 50milliwatts the helix voltage is reduced by 10 volts andv assumes thevalue 1465 volts. The output level is. thenraised to 60 milliwatts. i

With another tube, the curvemightbe-displaced to the left, for example;that is to say, the graduation borne by OWe would be displaced to theright so as to reach OW'e. The representativepoint corresponding to asignal of the same input power 5 milliwatts as before and to the sameoutput power of 70 milliwatts is at B on the curve 28 corresponding to ahelix voltage of 1455 volts. Now, the curves of the feedback loop nothaving changed, a helix voltage of 1475 volts would correspond to anoutput signal of 70 milliwatts. Assuming this to be the case, the pointB will therefore be moved towards the point A at the intersection of thestraight lineof abscissa 5 milliwatts and of the curve 22. It will stopat the point C of ordinate 50 milliwatts on the curve 29 of the helixvoltage, of 1465 volts. The regulation which previously took place aboutthe level of70 milliwatts, will be set up about the level of 60milliwatts with the new tube.

The regulating arrangement according to the present invention which isnow to be described has the essential feature that it supplies an output signal level which is completely independent both of the precisecharacteristics of the loops and of the detectors and amplifiersemployed. A variation of the characteristic curves of the latter can atthe most slightly modify the point of adjustment of the helixvoltageabout the optimum, but the corresponding variation of output level isquite negligible. r

Figure 5 illustrates an embodiment of the present invention, in whichthere are provided two traveling-wave tubes 550 and 520 having cathodes5M and 52l, and accelerating electrodes 502, 553, 522 and 523 of theelectron guns, 504 and 524 are the lines having a low velocity ofpropagation, constituted by helices, 565 and 525 are hollowcylindro-conical end members for the adaptation of the output circuitsto the helix, 506 and 526 similar cylindro-conical end members for theadaptation of the circuits to the helix and 557 and 521 targetscollecting the electrons of the electron beams after they have passedthrough the helices. The first tube 550 only plays the role of anamplitude-.modulator and. may be replaced by any suitable modulatingagency.

The input and output lines for the energy are coaxial lines 558, 559,528 and-529, the outer conductor of which is connected to the screenings5l2, 532 of the tubes-and the internal conductor .of which is.terminated by plates such as 5H), 51!, 530 and 53l capacitively coupledwith the cylindro-conical end members. 1 5l3'and 533 are thebeam-focussing coils,

514 is a source ,of alternating current for the heating of the cathode521 of-the tube 520. Series-connectedbatteries such as 5l5, 515, 5!!supply the various positive D. C-voltages necessary to the system andare provided with a hum-,- ber of tappings to this effect. Thus thecathode 521 is connected through connection 535 tothe negative terminalof 515, while the first accelerating electrodev 522, the secondaccelerating electrode 523, the helix 524 andthe target 52 1 arerespectivelyifedzfrom the batteries 5H5 to 511 through the connections536, 531, 538,- 539.

Similarly, 534 is "asource of alternating 'current for heating thecathode of the tube500; The cathode, the first accelerating-electrode502 the second accelerating electrode 503, the helix 504 and thetarget'5ll1 'are fed through the connections515, 516, 511,518 'and'519.

The element 550 is a low-frequency oscillator generating a signal offixed-frequency of the order ofsome hundredcycl'es per second, forexample, which is supposed to be lower than the lowest modulationfrequency present in the signals amplified by both :the tubes 500 'and520.

This signal is applied through a transformer 55! to the first anode 502of 'the traveling-wave tube 500 which amplifies: the ultra-highv:frequency signal received through the coaxial input line 508.

It will be seen-from the curvesillustrated in Figure 1, that, since thepotential of the anode 502 varies at the-frequency f,- the signalleaving the tube 500 through the coaxial output line 509 will beamplitude-modulated at thefrequency 3 about an average value equal tothe output power We corresponding to thein'put'power We.

The output signal of th'e -tube 500 is then: applied by thecoaxial-input line 528 constituting the extension of the coaxial outputline 509 to the input of the tube 520 constituting the factualregulating tube of thearrangement.

Referring to theFigure 2 it will readily besseen that:

If the voltage ofth'e helix 52 i i's fixed at' 'the potential of 1475volts giving the maxi-mumio'utput power, that is100milliwatts, for -'a'signal of given mean input powergfor example Qimilliwatts, the amplitude-m'odulation o'fj'thissinput signal at thefrequencygfj between thestraight lines 20I and 202 will give an'amplitude modulm tion of theoutput signal at -the' rrequency 2) between the straight'lines'iflt and204;

If the voltage ofthe helix 52'4 islo'wer -than the previous value,called the 1.-optimum-value, and is equal for example "to -l45(l volts,the same amplitude modulation of the input sig'nal will give anamplitude modulation ofthe output signal between the straight lines QOSan'd ZOB, constituted by an amplitude modulation of the frequency 2superposed'on an amplitude modulation at the frequency f in-phase withthe modulation of the input'sig'nal; v

If the voltage of the helix 51M i's h'igher than the previous value-andis 'eq ual 'for Ie'xample to 1500 volts, the same amplitude modulationof the input signal will give an amplitude moclulation of the outputsignal between the 'strai'ght': lines 201 and 288, constituted by anamplitude anodulation at the frequency 2 f superposedt'on Jan ramplitudemodulation at the frequency f in 'phase opposition to the modulation ofTthe' i-nput signal.

A fraction of the output signal, llaving the amplifier tube 52D'th'roughthe-' coaxialoutput line 529, is caught by--th'e loop 552 and-detectedby the detector 553'. 'The detecliedveltage amplified in the amplifier 554, which is pref'erably selective and tuned to 'the frequency film theoutput line 555 of thesa'id' amplifier there .is available an'amplified-sighal of frequency f,

'which'is-in phasewith, or in phase'oppositionto the signalgenerated bythe oscillator 550 accord- --ing to whetherthe voltage of thehelix52'4fis lower or higher than theoptimum voltage (neglecting theslight phase displ'acem'ents in transmission throughtheamplifier '5 54)The output signals of frequency f of the amplifier 554 and of theoscillator 550 are applied through the connections555 and 556 toe phasedetector device 551 which imparts to the output connections :558 apositive voltage if the-two signals are in phase, a negative voltage ifthese same signals are in phase opposition and-a zero voltage if thesignal from 554 is zero. :Phase detectorshaving these'propertiesare=well known in the art.

The voltage set up along the outputl-ine 558 is amplified'in a directcurrent amplifier 559 and the voltage delivered 'by -559 is applied:between the points 543 and 544, that is to say, it serves to adjust thevoltage of the helix 524 of the tube 520.

If it is 'assumed'that the voltage of the helix 524 is lower than theoptimum voltage, the signals in555 and 556 are in phase; thevoltagedelivered by 551 will be positive, as also will be the voltage deliveredby 559, and the voltage of the helix will rise to its optimum value.

Assuming now that the voltage of the helix "524 is higher thanthe-optimum voltage; the

signals in .555 and 556 are in phase opposition; the voltage deliveredby 551 will be negative as also will he the voltage delivered by;559 andthe voltage of the helix will fall to its 'optimum value.

, Regulation is therefore effected at the optimum voltage and the outputlevel is completely independent of the characteristic "curves of'the.loop

.matched so that it may not be the cause of stationary waves in the saidline. However, these conditions are in no way essential as they would bein the arrangement illustrated invFigure 4, in which, more particularlyif the line 409' were not matched, it would be essential for theloop tobe of the directional coupler type. In the regulating arrangement of thepresent invention, such a'type of loop isnot required.

The arrangements such as 551,- hereinabove called phase detectors bymeans of which it is possible toobtain, from an alternating-currentsignal of given frequencyya direct-current signal of proportionalamplitude-the polarity of which is positive ifthesaidalternating-current signal is in phase witha reference signal of equalfrequency; andthepolarity of which is negative if thealternating-currentsignal is in phase opposition to the referencesignal, are well known in the art. In order to render therspecificationcomp1ete',--Figure -6 illustrates-such an arrangement.

In Figure 6, :thesignal of which it is desired to detect the'phaserelatively to the reference signal, is applied through connections 555to the primary winding of a-transformertlll comprising a mid-pointsecondary winding. The

voltage of'each half ofthe secondary winding isrectified in diode 692and 603 and then-applied to resistances 604' and -605 .andfiltered bycondensersfiflfi and-601. Thediodesfifll and 603, "the resistances lilll and 605 and .the condensers 506 and; B0 1 are. identical in :pairs.

The signal. of.,.which the phase serves .as areferenceisappliedthroughcomiections -556to the primary winding of a. transformer608,- the secondary winding of,which is .inserted between a common-point609 .ofthe resistances' 604 and 605 andlofthecondensers 606 and 60"! anda j mid-pointfilfl ofl'th'e, secondary winding 'of the transformertlll.Under these conditions, there "ceives as reference frequency] signal the2f fre--' is obtained across the'ter'minalsiof an output line 558 a a.fdirectcurrent voltage substantially proportional to the amplitude .ofthe signal ape plied at555. andthe polarity of which depends upon thephase relationshipbetween the signal applied through 555 and thereference phase signal. ,7

With the f arrangement illustrated -in" Figure 5, it is possible;inaccordancewiththe example given, to obtain 'an'routputlevel constantto within 0.03%when theinput 'levelvaries-by about 5%. Thearrangementdescribed*with' reference to Figure r'enablestherange'of-variation-of the input signal to bevaried up -to about 50%."This arrangement'is characterizedby a cascade connection -of-twoarrangements of f the type illustrated on Figure Referringto Figure7-element 750 is alowfrequency oscillator generating a signal of fixedfrequency--f-.-- This signal is applied through a transformer I51 toalfirstanode lllz of a traveling-wave modulating tube-100,- whichamplifies the ultra-high frequency signal receivedby a coaxial inputline 108? The signal-leaving the tube IOU through-a coaxial output line109 a is amplitude-modulated at the irequency f. This signal is thenapplied through -a-coaxial input line 128. forming an extension of theline -109-to-the input of a tube A fraction of the output signalleavingthe amplifying tube -'I20throiigh a coaxial output line I29 is caughtbya 10013152, detected by a detector I53, amplified in a selectiveamplifier 154- (tuned to the frequency f) andapplied to a phase detectorIfil which also receivesa phase reference signal comingfrom the.oscillator 150.. v

The output signalfrom 151 is amplified by a V direct-current amplifierI59 andapplied between a helix I24 and thehigh voltage lead I44.

Element: 180 isea isecondlowefrequency oscil= lator generating-sa-signal ofxfixed frequency f diiferentfromrf. This signalis appliedthrough a transformer 'IBI to a first anode I22 of thetraveling-'wave-tube 120. The'signal leaving the tube lzfl throu'gh.the-coaxial output line I29 is applieditoia tube I80 through an'rinp-utline I98 of the tube. I99 =forming. .an .exte'nsioniof the line I29.

A fraction ioi the output signal leaving the.

amplifying; tube multhrougha coaxial output line 'Ifilluis 'caught byial loop It'i2,idetectedv by a detector 1163,"amplified:.in a selectiveamplifier I65 tuned: to the frequency ifl and applied tov a phasedetector I61.which'alsosreceivesa phase reference signal from anoscillator I80.- The output signal from 161113 amplified .by adirectcurrent amplifier I69 and applied between the helix I94 of thetube .190 and the high voltage lead I44.

Figure 8 illustrates an arrangement similar to that of Figure '7, but inwhich the oscillator I80 at the frequency f is omitted and in which aharmonic of frequency 2 of the frequency I used for the first tube I00is directly employed as modulation frequency for the second tube I20.

The oscillator 75!} then simultaneously produces the frequencies f and2) which are filtered pairs of quency signal from the filterI49in'steadof re-" ceiving the frequency j'.. A

It has. hitherto been assumed'that-th'e'charac- 1 teristic'curves ofFigure. 2 had maxima of equal ordinates foraconstant.:first=anode--voltage. It may happen; as illustrated inFigured, that the" 7 maximum constant ordinate is obtained;- not'atdifierent values of the helix voltage; with-"the'first anode voltagemaintained constant,"but with helix voltage first-anode voltage values,and even with combinations of "heli'x""'- voltage-first-anodevoltage-sec'ond-anode volt age values.

In Figure 3, for example, the curve 3I corresponds to a helix voltageof1500 volts and to a first-anode voltageofSO volts, the curve -32-to ahelix voltage of 1450 volts and to a first-anode voltage'of '70 volts,and the curve 33'toahelix voltage of H00 volts and to"a'first-anodevolt--- age of 60 volts.

It is therefore no longer sufiicient to act-only? on thevalue of thehelix voltage in order'to regulate the output power We to amaximumcorresponding to the mean value of the input power We modulatedin amplitude, but it is neces sary to actat the same time on thefirst-anode I voltage. For this purpose, the direct-current am-*-plifier '559 of Figure 5; comprises two outputs supplying directlyproportional voltages; Em-

ployment is made of the'fact that; inorder to'-' pass from-the curve 3|"to the curve 32"o'f-Figure= 3, the helixvoltagevaries-byvolts'and'the"; first-anode voltage by -l0 volts in the example1 illustrated. -It will therefore'be sufficient to take from a voltagedivider, to the terminals of which 3 1 r a helix correctionvoltage'willbe applied; a-volt-- age proportional to the said correction voltage andequal to "of its "value in" ordertoobtainthe firsteanode correctionvoltage.

It has been assumed-in Figure 3 that the char acteristic curvescorrespondingto a constant h' li x:

voltage and to decreasing first-anode'voltages voltage 70 volts), 35.(helix voltage 1500 volts;

first-anode voltage voltS) etc. Consequently, with a constant "inputpower-We the/outp t power is always an increasing-"fu t l first-anodevoltage:

On the other hand, with-certain tubes it may happen that. thecharacteristic curves correspo ng to a common helix voltageand. jt'o difirst-anode voltages intersect oneanotheri "This spending valuesare:

Curve 9|: Helix voltage 31500"voltsyfirsts volta '80 volts; "curve 92:"Helix voltage '1500" r the first anode 502, but to the first anode 522.

i were substantially parallel curves not intersectin one another, suchforexample-as the curves 3| (helix voltage 1500Ivolts, firstanl'ade'--voltage*80 volts), 3 t (helix voltage 1'50'0 volts;first-anode" case is illustrated'onFigui- 9; wh m..

For this purpose, the connection 518 is broken and the connection 536,instead of being connected directly to the battery is connected to thesecondary winding of the transformer 55! (connection 536 illustrated indot-and-dash lines). In addition, the tube 506 is omitted and the inputsignal is applied directly to the line 528.

Assuming now that the helix voltage is 1450 volts and that thefirst-anode voltage varies at the frequency 3 between '70 and 80 volts,the power of the output signal will be modulated at the frequency f andits amplitude will be represented by a point between the straight lines90! and 902. This modulation will be in phase with the modulation of thefirst-anode voltage. In fact, when the latter voltage reaches itsmaximum value of 80 volts, the representative point for an input signalof power we is at 95, at which the power of the output signal reachesits maximum value.

It it is now assumed that the helix voltage is 1 1500 volts, and thefirst-anode voltage varies at the frequency f between '70 and 80 volts,the power of the output signal will be modulated at the frequency f andits amplitude will be between the straight lines 903 and 904. Thismodulation will be in phase opposition to the modulation of thefirst-anode voltage. In fact, when the latter voltage reaches itsmaximum value of 80 volts the representative point for an input signalof the same power we as before is at 96, at which the power of theoutput signal reaches its maximum value.

In the first case, the helix voltage will increase, and in the secondcase it will decrease. This voltage will be fixed, for example, at avalue of 1475 volts, at which the point of intersection of the curves 9!and 98 corresponding to a common helix voltage of 1475 volts and tofirst-anode voltages of 80 and 70 volts respectively will be situated onthe straight line 99 of abscissa we.

Although the present invention has been de scribed with reference tocertain specific examples, its scope is sufficiently defined in theforegoing to enable the person skilled in the art to apply it to anyamplifying system in which traveling tubes are employed.

What I claim is:

1. An ultra-high frequency amplifier and power regulating systemcomprising at least one amplifying and regulating stage comprising atraveling wave-tube including at least a cathode for emitting electrons,an electron gun for forming an electron beam, said electron gunincluding at least one accelerating electrode, a low velocity ofpropagation transmission line having input and output terminals andadapted to have said electron beam pass therethrough, and an electroncollecting electrode, a load circuit connected to said output terminalsof said line, a source of ultrahigh frequency signals to be amplified, alow frequency alternating voltage source, an amplitude modulator fed onone hand by signals from said source of ultra-high frequency signals andon the other hand by an alternating voltage from said low frequencysource and delivering at its output ultra-high frequencyamplitude-modulated signals, means for impressing saidamplitudemodulated ultra-high frequency signals upon said inputterminals of said low velocity of propagation line, and a feedback loopcomprising an ultra-high frequency coupling circuit coupled to abovesaidload circuit, a detector fed from said coupling circuit and deliveringat its output low frequency detected signals, a low frequency amplifierhaving input terminals fed from output of said detector and deliveringatits output an amplified low frequency signal voltage, a phase detectorhaving a first and a second pair of input terminals and a pair of outputterminals, said first and second pair of input terminals beingrespectively fed from said amplified low frequency signal voltage andfrom a reference phase low frequency voltage from above-said lowfrequency alternating voltage source, said phase detector beingconstructed so as to deliver at its output terminals a rectifieddirect-current voltage of polarity depending upon the phase relationshipbetween voltages respectively applied to its first and second pair ofinput terminals, and means for applying said rectified direct-currentvoltage to above-said low velocity of propagation transmission line.

2. A system as claimed in claim 1, wherein a part of said rectifieddirect-current voltage is fed to an accelerating electrode of theelectron V gun of said traveling-wave tube.

3. A system as claimed in claim 1, wherein said amplitude-modulator isconstituted by an auxiliary traveling-wave tube having an alternatingcurrent voltage from said source of alternating current voltage appliedto an accelerating electrode of the electron gun of the said auxiliarytube.

4. A system as claimed in claim 1, wherein said low-frequency amplifieris a selective amplifier tuned to the frequency of said low-frequencyalternatin voltage source.

5. A system as claimed in claim 1, wherein said means for applying saidrectified direct-current voltage to said low velocity of propagationtransmission line of said traveling-wave tube comprises a direct-currentamplifier.

6. A system as claimed in claim 1, comprising two amplifying andregulating stages, wherein the low-frequency alternating voltage sourcesrespectively pertaining to each stage have difierent frequencies,

7. A system as claimed in claim 6, wherein the frequency of one of saidtwo low-frequency alternating voltage sources is equal to twice thefrequency of the other low-frequency alternating voltage source.

8. A system as claimed in claim 7, wherein said alternating voltagesource having a frequency equal to twice the frequency of the otherlow-frequency alternating voltage source consists in a filter tuned tothe second harmonic of the frequency of and fed from said otherlow-frequency alternatin voltage source.

PIERRE MARCEL LAPOSTOLLE.

No references cited.

